JP5558866B2 - Water treatment apparatus and water treatment method - Google Patents

Description

  The present invention relates to a water treatment apparatus and a water treatment method, and more particularly to a water treatment apparatus and a water treatment method for removing a fluorine component and a nitrogen component from water to be treated containing a fluorine component and a nitrogen component.

  Fluoric acid, ammonia, nitric acid, etc. are used in metal surface treatment processing factories and IC and other semiconductor device manufacturing factories, so fluorine components (fluorine ions) and nitrogen components (ammonium nitrogen, nitrous acid, nitrate) Waste water containing inorganic nitrogen such as nitrogen is generated.

  When discharging such waste water into the environment, it is necessary to treat the concentration of the fluorine component and the nitrogen component to be equal to or lower than predetermined concentrations. As a method for removing fluorine components from wastewater (hereinafter referred to as treated water), a calcium agent (calcium hydroxide, calcium chloride, etc.) is added to the treated water, and fluorine components (fluorine ions) in the treated water There is known a method of removing fluorine components from water to be treated by binding calcium ions to precipitate calcium fluoride and precipitating and separating the calcium fluoride.

The precipitated calcium fluoride is in an equilibrium state in water as shown in the following reaction formula.
CaF ₂ ⇔ 2F ⁻ + Ca ²⁺
For this reason, precipitation of calcium fluoride does not proceed sufficiently by adding calcium ions in an amount corresponding to fluorine ions (1 mol of calcium ions per 2 mol of fluorine ions), and the fluorine component is effective from the water to be treated. It is difficult to remove it. Therefore, in order to effectively remove the fluorine component from the water to be treated, it is necessary to add an excess amount of calcium ions than the amount corresponding to the fluorine ions.

  On the other hand, as a method of removing the nitrogen component, a method of biologically removing the nitrogen component using a microorganism is known. For example, when the nitrogen component is nitrous acid or nitrate nitrogen, a method is known in which nitrous acid or nitrate nitrogen is reduced together with a hydrogen donor such as methanol by denitrifying bacteria and removed as nitrogen gas. In addition, when the nitrogen component contains ammonium nitrogen, the ammonium nitrogen is oxidized to nitrite and nitrate nitrogen by nitrifying bacteria, and then the nitrous acid and nitrate nitrogen are denitrifying bacteria together with a hydrogen donor such as methanol. There is known a method of reducing the nitrogen gas as nitrogen gas.

  Usually, when removing fluorine components and nitrogen components from the water to be treated as described above, the fluorine components may adversely affect the biological treatment ability of nitrifying bacteria and denitrifying bacteria. A water treatment apparatus configured to remove the nitrogen component after the removal is used. The water treatment apparatus includes a fluorine treatment unit that removes a fluorine component and a nitrogen treatment unit that removes a nitrogen component.

  However, in the first treated water from which the fluorine component has been removed in the fluorine treatment section, a large amount of calcium ions that did not precipitate as calcium fluoride remain, and such first treated water is introduced as it is into the nitrogen treatment section. When this is done, nitrogen removal by microorganisms in the nitrogen treatment section is usually suitably carried out at a neutral to weakly alkaline pH, so that calcium ions bind to other ions and precipitate as inorganic solids within the pH range. There is a problem that it is unavoidable.

In such a case, since the density | concentration of an inorganic solid substance will increase in a nitrogen treatment part, there exists a possibility that the processing capacity of a nitrogen treatment part may fall and it may become difficult to perform an effective process.
Further, when fluidized bed processing is performed in the nitrogen processing section, there is a problem in that calcium salts are deposited on the surface of the carrier in the nitrogen processing section, the surface of constituent devices such as a stirrer and a diffuser, and the respective functions are lost. is there.
For this reason, there is a known method for removing calcium ions by providing a Ca removal unit for removing calcium ions from the first treated water before being introduced into the nitrogen treatment unit, and precipitating calcium salts with carbonate ions or phosphate ions. (Patent Document 1).

JP 2001-276851 A

  However, when calcium ions are removed as described above, a large amount of precipitates (solid matter) such as calcium carbonate is generated. Therefore, the precipitates are separated, dehydrated, and discarded. It takes time and money. Moreover, since it is necessary to provide a Ca removal part in addition to the fluorine and nitrogen treatment parts, and facilities for separating and dehydrating precipitates are also required, the water treatment apparatus becomes large. .

  Therefore, in view of the above problems, the present invention can easily remove the fluorine component and the nitrogen component from the water to be treated while suppressing the amount of solid matter generated, and can be treated without increasing the size of the equipment. It is an object of the present invention to provide a water treatment apparatus and a water treatment method capable of treating water.

As a result of extensive research by the present inventors, when removing the nitrogen component from the water to be treated from which the fluorine component has been removed , the pH of the mixed water containing the water to be treated and the microorganisms is adjusted to a predetermined range, and the carrier By using a fluidized bed type treatment using microorganisms that are supported or aggregated on the surface, it is possible to effectively remove nitrogen components from the water to be treated even in a state containing calcium ions. The present inventors have found that this can be done and have completed the present invention.

That is, the water treatment apparatus according to the present invention is a fluorine treatment in which calcium ion is added to water to be treated containing a fluorine component and a nitrogen component to precipitate calcium fluoride, and the fluorine component is removed to obtain first treated water. and parts, the water treatment device in which a nitrogen processor to obtain a second treated water by removing nitrogen components from biologically first treated water by microorganisms,
The nitrogen treatment unit includes a nitrification tank that oxidizes ammonia nitrogen in the first treated water by the nitrifying bacteria as the microorganism, and a denitrifying bacterium as the nitrogen component in the first treated water treated in the nitrifying tank. A denitrification tank that reduces by nitrogen and removes it as nitrogen gas,
In the nitrification tank, fluidized bed type treatment using either one or both of a microbial support in which the nitrifying bacteria are supported on a carrier surface and a microbial aggregate formed by aggregation of the nitrifying bacteria themselves is formed. Configured to be performed, and configured to maintain the pH of the mixed water containing the first treated water and the nitrifying bacteria at 5 to 6.5,
The denitrification tank is a fluidized bed type using either one or both of a microbial carrier in which the denitrifying bacteria are supported on a carrier surface and a microbial aggregate formed by aggregation of the denitrifying bacteria themselves. It is configured to perform the treatment, and the pH of the mixed water is maintained to be less than 7 so that the Langeria coefficient of the mixed water containing the first treated water and the denitrifying bacteria is −0.5 to 0. It is comprised in that .

According to such a configuration, when the fluorine component is removed by calcium ions in the fluorine treatment unit, it is necessary to add an excessive amount of calcium ions to the fluorine component. Contains calcium ions. Then, such first treated water is introduced into a nitrogen treatment section that performs fluidized bed processing using either one or both of the microorganism carrier and the microorganism aggregate, and is a mixed water containing the first treated water and the microorganisms. By maintaining the pH at such a level that the calcium salt does not precipitate, even in the first treated water containing calcium ions, the nitrogen component can be effectively removed without causing the calcium salt to precipitate.

For this reason, it is not necessary to remove calcium ions from the first treated water, and it is possible to eliminate the trouble and cost of separating, dehydrating and discarding calcium salt deposits, and to easily treat the treated water. Can do. In addition, it is not necessary to provide a Ca removing unit for removing calcium ions from the first treated water in front of the nitrogen treating unit , and no facility for separating and dehydrating precipitates is required. Can do.

In detail, when removing nitrogen components using microorganisms related to nitrogen removal, such as denitrifying bacteria and nitrifying bacteria, the treatment is usually carried out by adjusting the pH of the mixed water to a weakly alkaline pH that increases the activity of the microorganisms. However, at such a pH, calcium ions in the first treated water are likely to bind to other ions and precipitate. However, by maintaining the pH of the mixed water to such an extent that the calcium salt does not precipitate, the nitrogen component can be removed while suppressing the precipitation of the calcium salt. Accordingly, even in the case of using the fluidized bed process in a nitrogen processor, inhibiting calcium salt to the surface of the device for creating a fluidized bed of the carrier surface and an agitator, etc. in nitrogen processor that precipitated It is possible to prevent the performance of the carrier and the device from being hindered by the calcium salt, and it is possible to prevent the processing ability of the nitrogen treatment unit from being lowered.

On the other hand, by adjusting the pH of the mixed water as described above, the treatment capacity of the microorganism itself in the nitrogen treatment section will be reduced, but the microorganism is supported on the carrier or the microorganism itself is aggregated By performing the fluidized bed treatment, microorganisms suitable for nitrogen treatment on the support surface and aggregates can be selectively maintained at a high density. For this reason, the amount of microorganisms suitable for nitrogen treatment per unit volume can be increased as compared with the case where the microorganisms themselves are dispersed in the mixed water (floating sludge method). Moreover, the separation of the second treated water and the microorganisms (in a state of being supported on the carrier surface or agglomerated) can be performed effectively, and the amount of microorganisms flowing out together with the second treated water is determined by the floating sludge method. Can also be reduced. For this reason, it can suppress that the microorganisms concentration in a nitrogen treatment part falls. Further, since precipitation of the calcium salt is suppressed, the calcium salt does not adhere to the microorganism carrier or the microorganism aggregate, and the management of the amount of microorganisms in the nitrogen treatment unit is facilitated.

As described above, since the concentration of microorganisms suitable for nitrogen treatment can be increased in the nitrogen treatment section , and the outflow amount of microorganisms can be reduced, the microorganisms suitable for nitrogen treatment can be maintained at a high concentration. Can do. For this reason, it is possible to effectively remove the nitrogen component even in an environment where the processing ability of the microorganism is lowered (pH at which calcium salt does not precipitate). Therefore, it is not necessary to remove calcium ions from the first treated water, and there is no need to provide a Ca removing unit, so that the water to be treated can be easily treated while suppressing the amount of solid matter generated, and the water treatment The apparatus can be miniaturized.

Moreover, when the ratio of the amount of microorganisms in the nitrogen treatment part is lower than a predetermined ratio with respect to the amount of nitrogen component in the first treated water, the content of calcium ions is smaller than that in the first treated water and contains the nitrogen component The acclimatized water is introduced into the nitrogen treatment unit instead of the first treated water, and the microorganisms are acclimatized until the amount of microorganisms in the nitrogen treatment unit reaches a predetermined ratio with respect to the amount of nitrogen components in the first treated water. It is preferable that it is comprised.

According to such a configuration, the conditioned water having a calcium ion content smaller than that of the first treated water is introduced into the nitrogen treatment unit in place of the first treated water, and therefore, compared to the case where the first treated water is introduced. The amount of precipitated calcium salt is reduced. Thereby, the microorganisms can be effectively propagated by maintaining the pH of the mixed water containing the microorganisms and the conditioned water at a pH at which the activity of the microorganisms is primarily increased. For this reason, the ratio of the amount of microorganisms with respect to the amount of nitrogen components in the first treated water can be increased in a shorter time than when the first treated water is introduced into the nitrogen treatment unit .

  Moreover, it is preferable that the pH of the mixed water in the period when acclimatization of microorganisms is performed is maintained at 7-9.

  Moreover, it is preferable that the content density | concentration of the calcium ion of 1st treated water is 200-5000 mg / L.

The water treatment method according to the present invention includes a fluorine treatment step in which calcium ions are added to water to be treated containing a fluorine component and a nitrogen component to precipitate calcium fluoride, and the fluorine component is removed to obtain first treated water. In a water treatment method comprising a nitrogen treatment step of biologically removing a nitrogen component from a first treatment water by a microorganism to obtain a second treatment water,
The nitrogen treatment step includes a nitrification step in which ammonia nitrogen in the first treated water is oxidized by nitrifying bacteria as the microorganism, and a nitrogen component in the first treated water treated in the nitrification step as a denitrifying bacterium as the microorganism. A denitrification step of reducing by nitrogen and removing as nitrogen gas,
In the nitrification step, fluidized bed type treatment using either one or both of a microbial support in which the nitrifying bacteria are supported on a carrier surface and a microbial aggregate formed by aggregation of the nitrifying bacteria themselves is formed. And maintaining the pH of the mixed water containing the first treated water and the nitrifying bacteria at 5 to 6.5,
In the denitrification step, a fluidized bed using either one or both of a microbial carrier in which the denitrifying bacterium is supported on a carrier surface and / or a microbial aggregate formed by aggregation of the denitrifying bacterium itself. And the pH of the mixed water is maintained at less than 7 so that the Langerian coefficient of the mixed water containing the first treated water and the denitrifying bacteria is -0.5 to 0. And

  When the proportion of the amount of microorganisms in the nitrogen treatment step is lower than the predetermined proportion with respect to the amount of nitrogen component in the first treated water, the acclimatization has less calcium ions than the first treated water and contains a nitrogen component. It is preferable to use water instead of the first treated water and acclimate the microorganisms until the amount of microorganisms in the nitrogen treatment step reaches a predetermined ratio with respect to the amount of nitrogen components in the first treated water.

  Moreover, it is preferable to maintain the pH of the mixed water at 7-9 during the period in which the microorganisms are acclimatized.

  Moreover, it is preferable that the content density | concentration of the calcium ion of 1st treated water is 200-5000 mg / L.

  As described above, according to the present invention, it is possible to easily remove the fluorine component and the nitrogen component from the water to be treated while suppressing the amount of solid matter generated, and to treat the water without increasing the size of the equipment. Can be processed.

(A) is a block diagram which shows the water treatment apparatus which concerns on 1st Embodiment (reference form) , (b) is a block diagram which shows the water treatment apparatus which concerns on 2nd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

<First embodiment (reference form) >
Hereinafter, the water treatment apparatus 1 concerning 1st Embodiment (reference form) is demonstrated, referring Fig.1 (a). The water treatment apparatus 1 is configured to remove the fluorine component and the nitrogen component from the water to be treated containing the fluorine component and the nitrogen component. The water to be treated by the water treatment device 1 is discharged from a surface treatment factory for metal materials, a semiconductor and IC raw material manufacturing factory, a coal-fired power plant, a glass processing factory, a liquid crystal display manufacturing factory, etc. Waste water.

  The concentration of the fluorine component contained in the water to be treated is, for example, a value higher than 15 mg / L, and the concentration of the nitrogen component is, for example, a value higher than 10 mg / L.

  The water treatment apparatus 1 is configured to remove the nitrogen component after removing the fluorine component from the water to be treated. Specifically, the water treatment apparatus 1 removes the fluorine component from the introduced treated water to obtain the first treated water, and removes the nitrogen component from the first treated water to obtain the second treated water. And a nitrogen treatment unit 3 for obtaining treated water. In addition, before to-be-processed water is introduce | transduced into the water treatment apparatus 1, it is accumulate | stored in a storage part (not shown), and it is preferable to introduce into the water treatment apparatus 1 quantitatively and continuously from there.

  In the fluorine treatment unit 2, calcium ions are added to the introduced water to be treated to remove the fluorine component. Specifically, the fluorine treatment unit 2 includes a reaction tank 21 in which calcium ions are added to the water to be treated, an aggregation tank 22 in which precipitates of fluorine components are aggregated, and the aggregated precipitates to be treated. And a fluorine separation tank 23 that is separated from water to obtain first treated water.

  The calcium ions added in the reaction vessel 21 are preferably added as a water-soluble calcium salt or an aqueous solution thereof. The calcium salt is not particularly limited, and calcium hydroxide, calcium chloride, and the like can be used. By adding calcium ions to the water to be treated, fluorine components (fluorine ions) in the water to be treated and calcium ions are combined to form calcium fluoride, which is precipitated in the water to be treated.

  Since the calcium fluoride is in an equilibrium state with fluorine ions and calcium ions in water, an amount of calcium ions corresponding to the amount of fluorine ions in the water to be treated (1 mol of calcium ions relative to 2 mol of fluorine ions) is added. Only by being done, the fluorine ion in to-be-processed water cannot be effectively precipitated as calcium fluoride. For this reason, an excessive amount of calcium ions is added to the amount of fluorine ions. The addition amount of calcium ions is preferably 2 to 7 times the theoretically required amount with respect to the fluorine ion amount. Thereby, a fluorine ion can be effectively precipitated as calcium fluoride. In order to accurately control the amount of calcium ions to be added, the calcium ions are preferably added in the form of an aqueous solution of a calcium salt.

  The means for adding calcium ions is not particularly limited, but is preferably added from a chemical tank 24 in which a calcium salt or an aqueous solution thereof is stored. The chemical tank 24 is preferably configured to be able to supply calcium salt or an aqueous solution thereof to the water to be treated according to the fluorine ion concentration in the water to be treated.

  In the agglomeration tank 22, calcium fluoride precipitated in the water to be treated treated in the reaction tank 21 is agglomerated by various methods. For example, a method of aggregating calcium fluoride using a flocculant to form a floc can be employed. As the flocculant, aluminum flocculants such as aluminum sulfate, sodium aluminate and basic aluminum chloride, acrylic polymer flocculants such as sodium polyacrylate and polyacrylamide, and the like can be used. A flocculant may be used by 1 type and may be used together 2 or more types.

  In the fluorine separation tank 23, the calcium fluoride aggregated in the for-treatment water supplied from the aggregation tank 22 is separated from the for-treatment water by various methods. For example, the aggregate of calcium fluoride can be separated from the water to be treated using known solid-liquid separation means such as clarifier and thickener. Thereby, it becomes possible to make the fluorine ion concentration of the obtained 1st treated water 15 mg / L or less. In the first treated water, calcium ions that did not precipitate as calcium fluoride remain. The concentration of calcium ions in the first treated water is, for example, 200 mg / L or more, although it depends on the fluorine ion concentration in the treated water. The pH of the first treated water is 6-8.

  In the nitrogen treatment unit 3, the first treated water containing calcium ions is biologically treated by microorganisms to remove nitrogen components. Specifically, the nitrogen treatment unit 3 includes a denitrification tank 31 in which nitrogen components (nitrite and nitrate nitrogen) in the first treated water are reduced by microorganisms (denitrification bacteria) and removed as nitrogen gas, and nitrogen components A re-aeration tank 32 for decomposing and removing organic matter such as methanol in the first treated water from which the first treatment water has been removed; and a microorganism separation tank 33 for obtaining second treated water by separating microorganisms from the first treated water from which the organic matter has been removed; It has. Further, in the nitrogen treatment unit 3, the nitrogen component is removed while maintaining the pH of the mixed water containing the first treated water and the microorganisms so that the calcium salt does not precipitate. As pH of mixed water, it is preferable that it is less than 7, and it is more preferable that pH is 5-6.5 by the point which keeps the processing speed in the nitrogen treatment part 3 more favorable.

  In the denitrification tank 31, nitrogen components are removed as nitrogen gas by reducing nitrous acid and nitrate nitrogen in the first treated water by denitrifying bacteria in an oxygen-free atmosphere. The denitrification tank 31 is a fluidized bed type treatment using either one or both of a microbial carrier in which denitrifying bacteria are supported on the carrier surface and a microbial aggregate formed by aggregation of the denitrifying bacteria themselves. Configured to do. In the denitrification tank 31, the mixed water containing the first treated water and the denitrifying bacteria is mechanically stirred using a stirrer or the like, so that the microbial carrier and the microbial aggregate are fluidized in water to form a fluidized bed. ing. Further, the denitrification tank 31 is provided with solid-liquid separation means such as a screen so that the microbial carrier and the microbial aggregates do not flow out of the denitrification tank 31. In the present embodiment, the fluidized bed process includes an upward flow sludge blanket (USB) type.

  As the carrier on which the microorganisms are carried, it is preferable to use a carrier configured so that the specific gravity of the carrier itself is close to the specific gravity of water. For example, porous sand, activated carbon, resin or the like formed in a cylindrical shape or granular shape can be used. Specifically, it is a resin carrier having a cylindrical shape with a diameter of about 8 to 15 mm and a length of about 5 to 10 mm, and one or more partition plates are provided in the internal space. Things can be used. In addition, a resin carrier having a cylindrical shape such as a cylinder or a quadrangular column, or a gel-like carrier molded in a granular shape or a grid shape can be used. By using these carriers, the microorganisms are supported on the surface of the carrier in the form of a film, so that the amount of microorganisms per unit volume can be increased as compared with the case where the microorganisms are dispersed in water (floating sludge method).

  On the other hand, it is preferable to use a microorganism aggregate formed so as to have a specific gravity close to that of water. Microorganism aggregates are those grown in granular form (granular form) by the self-granulating action of microorganisms, or those in which microorganisms are grown in granular form using an aggregating agent, etc., with microorganisms supported on a carrier The amount of microorganisms per unit volume can be increased.

  An organic substance is supplied to the denitrification tank 31 as a hydrogen donor. The organic matter is used not only as a hydrogen donor when denitrifying bacteria reduce nitrous acid and nitrate nitrogen, but also as a substrate when denitrifying bacteria grow. As the organic substance, chemicals such as methanol and acetic acid can be used, and the BOD component in the first treated water can also be used. For the purpose of accurately controlling the amount of organic substance to be added, it is preferable to use a liquid organic substance.

  The means for supplying the organic matter is not particularly limited, but an organic matter supply tank 34 configured to be able to control the amount of the organic matter supplied according to the concentration of nitrous acid or nitrate nitrogen in the first treated water. It is preferable to use it.

  Further, in the denitrification tank 31, the pH of the mixed water containing the first treated water and the denitrifying bacteria is maintained at such an extent that the calcium salt does not precipitate (preferably less than 7, more preferably 5 to 6.5). . Specifically, the pH at which the calcium salt does not precipitate is calculated from the calcium saturation index (Langeria index) calculated from the calcium concentration, soluble salt concentration, M alkalinity, liquid temperature, etc., and the calcium saturation index -0.5 to The pH in the tank is controlled so as to be within the range of 0.

As a result, the activity of the denitrifying bacteria is reduced, but the amount of denitrifying bacteria per unit volume in the denitrifying tank 31 is determined by the floating sludge method because the denitrifying bacteria are in the form of a microorganism carrier or microbial aggregate. It can be increased than in the case of. For this reason, it is possible to effectively reduce nitrous acid and nitrate nitrogen, and it is possible to effectively remove the nitrogen component as nitrogen gas.
In the denitrification tank 31, hydroxide ions are generated due to reduction by denitrifying bacteria, and the pH rises. Therefore, an acid such as hydrochloric acid is added as necessary to maintain the pH below 7. Is done. In addition, as an acid, the sulfuric acid etc. which produce a hardly soluble calcium salt are not preferable, and it is preferable to use hydrochloric acid which does not produce a hardly soluble salt.

  The re-aeration tank 32 is configured such that organic matter remaining in the first treated water treated in the denitrification tank 31 is decomposed by aerobic microorganisms. Thereby, it is possible to prevent the organic matter from being discharged into the environment while remaining in the treated water. The pH in the re-aeration tank 32 is adjusted to be equal to the pH in the denitrification tank 31 so that the calcium salt does not precipitate. The re-aeration tank 32 may be either a fluidized bed type or a floating sludge method, but it is preferable to adopt a fluidized bed type.

  In the microorganism separation tank 33, microorganisms are separated from the first treated water (denitrification treated water) treated in the re-aeration tank 32 after being treated in the denitrification tank 31 by various methods. Microorganisms in the denitrified water can be easily separated using a known solid-liquid separation means such as a clarifier or thickener. Thereby, the 2nd treated water whose nitrogen ingredient concentration is 10 mg / L or less is obtained. The second treated water may be discharged into the environment (to a river or the like) as it is if it satisfies other water quality standards, or may be sent to another water treatment device for treatment. The pH of the second treated water may be within a range where it can be discharged (specifically, pH 5.8 to 8.6). However, as with the denitrification tank 31 and the re-aeration tank 32, precipitation of calcium salt is possible. It is preferable to maintain the pH at which no occurrence occurs.

<Second Embodiment>
Hereinafter, the water treatment apparatus 10 according to the second embodiment will be described with reference to FIG. Compared with the water treatment apparatus 1 concerning 1st Embodiment (reference form) , the water treatment apparatus 10 concerning 2nd Embodiment mainly differs in the structure of the nitrogen treatment part 30. FIG. Therefore, below, it demonstrates centering on a different point from 1st Embodiment (reference form), and it abbreviate | omits description as attaching | subjecting the same code | symbol to the same structure.

In the nitrogen treatment unit 30, the first treated water containing calcium ions treated in the fluorine treatment unit 2 is treated by microorganisms to remove nitrogen components (including ammonia nitrogen). Specifically, the nitrogen treatment unit 30 includes a nitrification tank 35 in which ammonia nitrogen in the first treated water is oxidized by microorganisms (nitrifying bacteria) before the denitrification tank 32. That is, the nitrogen treatment unit 30 removes ammonia nitrogen, nitrous acid, and nitrate nitrogen as nitrogen components. Further, in the nitrogen treatment unit 30, as in the first embodiment (reference form) , the nitrogen component is removed while maintaining the pH of the mixed water containing the first treated water and the microorganisms so that the calcium salt does not precipitate. It is. The pH of the mixed water is preferably less than 7 and more preferably 5 to 6.5.

  In the nitrification tank 35, ammonia nitrogen is oxidized to nitrite or nitrate nitrogen by nitrifying bacteria in an aerobic atmosphere. The nitrification tank 35 is subjected to fluidized bed processing using either one or both of a microbial support in which nitrifying bacteria are supported on the carrier surface and / or a microbial aggregate formed by aggregation of the nitrifying bacteria themselves. It is configured as follows. In the nitrification tank 35, aeration is performed in the mixed water containing the first treated water and the denitrifying bacteria, whereby the microbial carrier and the microbial aggregate are flowed in water to form a fluidized bed. Further, the nitrification tank 35 is provided with solid-liquid separation means such as a screen so that the microorganism carrier and the microorganism aggregates do not flow out of the nitrification tank 35.

  As the carrier for supporting nitrifying bacteria, the same carrier as that used in the denitrification tank 32 can be used. As the microbial aggregate, those having the same properties as those in the denitrification tank 32 can be used except that nitrifying bacteria are aggregated.

Moreover, in the nitrification tank 35, similarly to the denitrification tank 31, the pH of the mixed water containing the first treated water and the nitrifying bacteria does not precipitate calcium salt (preferably less than 7, more preferably 5-6. 5). As a result, the activity of nitrifying bacteria is reduced, but the amount of nitrifying bacteria per unit volume in the nitrifying tank 35 is more than in the case of the floating sludge method because the nitrifying bacteria are in the form of microbial carriers or microbial aggregates. Therefore, it is possible to effectively nitrify ammonia nitrogen. Then, the first treated water treated in the nitrification tank 35 is introduced into a fluidized bed type denitrification tank 31 similar to the first embodiment (reference form), and a removal process of nitrous acid and nitrate nitrogen is performed. The second treated water and the microorganisms are separated in the microorganism separation tank 33 through the re-aeration tank 32.
The pH in the denitrification tank 31, the re-aeration tank 32, and the microorganism separation tank 33 is preferably adjusted to a pH at which calcium salt does not precipitate as in the nitrification tank 35.
Thereby, the 2nd treated water whose nitrogen ingredient concentration is 15 mg / L or less is obtained. The second treated water may be discharged into the environment (to a river or the like) as it is if it satisfies other water quality standards, or may be sent to another water treatment device for treatment.

  In the water treatment apparatuses 1 and 10 according to the first and second embodiments, the proportion of the amount of microorganisms in the nitrogen treatment units 3 and 30 is lower than a predetermined proportion with respect to the amount of nitrogen components in the first treated water. For example, immediately after the water treatment apparatuses 1 and 10 are newly installed (when the water treatment apparatuses 1 and 10 are started up), it is necessary to treat the water to be treated after sufficiently acclimatizing the microorganisms.

  In such a case, it is preferable to introduce the conditioned water that can efficiently acclimate the microorganism into the nitrogen treatment units 3 and 30 instead of the treated water. As the conditioned water, it is preferable to use one having a calcium ion content smaller than that of the first treated water and containing a nitrogen component. Thereby, acclimatization of microorganisms can be performed efficiently until the amount of microorganisms reaches a predetermined ratio with respect to the amount of nitrogen components in the first treated water. The pH of the mixed water during the period of acclimatization of microorganisms is preferably maintained at 7-9. Thereby, acclimatization of microorganisms can be performed more efficiently.

  As described above, according to the water treatment apparatus of the present invention, it is possible to easily remove the fluorine component and the nitrogen component from the water to be treated while suppressing the amount of solid matter generated, and increase the size of the facility. The treated water can be treated without any problems.

  That is, the water treatment apparatuses 1 and 10 are configured to perform a fluidized bed type treatment using the first treated water containing calcium ions using either one or both of the microorganism carrier and the microorganism aggregate. The first treated water containing calcium ions introduced into the parts 3 and 30 and maintaining the pH of the mixed water containing the first treated water and the microorganisms to such an extent that the calcium salt does not precipitate (preferably less than 7). Even so, the nitrogen component can be effectively removed without precipitating the calcium salt.

  For this reason, it is not necessary to remove calcium ions from the first treated water, and it is possible to eliminate the trouble and cost of separating, dehydrating and discarding calcium salt deposits, and to easily treat the treated water. Can do. Further, since it is not necessary to provide a Ca removing unit for removing calcium ions from the first treated water in front of the nitrogen treating units 3 and 30 and no facility for separating and dehydrating the precipitate is necessary, 10 can be reduced in size.

  More specifically, by adjusting the pH of the mixed water to such an extent that calcium salt does not precipitate, the treatment capacity of the microorganisms themselves in the nitrogen treatment units 3 and 30 will be reduced. By performing the fluidized bed process used, the density of the microorganisms on the surface of the carrier and the aggregates can be maintained at a high density. For this reason, the microorganisms in the nitrogen treatment units 3 and 30 can be maintained at a higher concentration than the floating sludge method. In addition, by performing fluidized bed type treatment using either one or both of the microbial support and the microbial aggregate, the separation of the second treated water and the microorganisms can be performed effectively, together with the second treated water. The amount of microorganisms that flow out can be reduced. Thereby, it can suppress that the density | concentration of microorganisms falls in the nitrogen treatment parts 3 and 30. FIG. Moreover, since the calcium salt does not adhere to the microorganism carrier or the microorganism aggregate, the management of the amount of microorganisms in the nitrogen treatment units 3 and 30 is facilitated.

  As described above, since the concentration of microorganisms in the nitrogen treatment units 3 and 30 can be increased and the outflow amount of microorganisms can be reduced, the concentration of microorganisms in the nitrogen treatment units 3 and 30 is higher than that in the floating sludge method. The concentration can be maintained. For this reason, it is possible to effectively remove the nitrogen component even in a state where the treatment ability of the microorganism itself is lowered (pH environment in which calcium salt does not precipitate).

Moreover, when the ratio of the amount of microorganisms in the nitrogen treatment units 3 and 30 is lower than a predetermined ratio with respect to the amount of nitrogen components in the first treated water, the conditioned water has a lower calcium ion content than the first treated water. Is introduced into the nitrogen treatment units 3 and 30 in place of the first treated water, so that even if the pH of the mixed water containing the microorganisms and the conditioned water is primarily maintained at a pH at which the activity of the microorganisms is increased, the first The amount of calcium salt deposited is reduced as compared with the case where treated water is introduced. For this reason, the growth of microorganisms can be performed efficiently, and the ratio of the amount of microorganisms to the amount of nitrogen components in the first treated water can be reduced in a shorter time than when the first treated water is introduced into the nitrogen treatment units 3 and 30. Can be increased.
The microorganism separation tank 33 of the first and second embodiments may be replaced with a membrane separation device.

  Next, the present invention will be described more specifically with reference to examples and comparative examples.

1. Examples 1 and 2
<Treatment water>
The water to be treated was one having a calcium ion concentration (Ca concentration) of 1000 mg / L and a nitrate nitrogen concentration (NO ₃ —N concentration) of 580 mg / L.
<Denitrification tank>
The denitrifying bacteria supported on the surface of the carrier was introduced into a denitrification tank and stirred using a stirrer to form a fluidized bed. Further, the inside of the denitrification tank was in an oxygen-free state. Incidentally, the volume load on the nitrate nitrogen (NO ₃ -N volume loading) are shown in Table 1 below.
<Carrier>
As the carrier supporting the denitrifying bacteria, a carrier formed using a resin material and having a specific surface area of 500 m ² / m ³ was used. In addition, the shape of the carrier is a cylindrical shape (inner diameter: 10 mm, length: 7 mm), and a cross-shaped partition plate is formed along the axial direction so as to divide the internal space. Using.
<Test method>
The treated water was introduced into the denitrification tank, and biological denitrification treatment was performed in a state where the pH of the mixed water of the denitrifying bacteria and the treated water was maintained at 6.0. Thereafter, mixed water was introduced into the precipitation tank, and the microorganisms peeled off from the carrier were separated from the mixed water to obtain treated water (fluidized bed type treatment method). And the removal rate of nitrate nitrogen was computed from following formula (1). The removal rate is shown in Table 1 below.

(Concentration of nitrate nitrogen in raw water-concentration of nitrate nitrogen in treated water) / Concentration of nitrate nitrogen in raw water (1)

2. Comparative Examples 1 and 2
<Treatment water>
The same water to be treated as in the example was used.
<Denitrification tank>
A denitrification tank was configured under the same conditions as in the Examples except that the denitrifying bacteria were directly dispersed in water. Incidentally, the volume load on the nitrate nitrogen (NO ₃ -N volume loading) are shown in Table 1 below.
<Test method>
The treated water was introduced into the denitrification tank, and biological denitrification treatment was performed in a state where the pH of the mixed water containing the microorganisms and the treated water was maintained at 6.0. Thereafter, mixed water was introduced into the sedimentation tank, and microorganisms were separated from the mixed water to obtain treated water (floating sludge method). And the removal rate of nitrate nitrogen was computed from following formula (1). The removal rate is shown in Table 1 below.

(Concentration of nitrate nitrogen in raw water-concentration of nitrate nitrogen in treated water) / Concentration of nitrate nitrogen in raw water (1)

3. Comparative Example 3
The test was conducted in the same fluidized bed type treatment as in the example except that the pH of the mixed water containing the microorganisms and the water to be treated was maintained at 8.0.

3. Summary When Table 1 is seen, the removal rates of Examples 1 and 2 are higher than those of Comparative Examples 1 and 2. This is because denitrifying bacteria are supported on the surface of the carrier as in the example, so that the amount of denitrifying bacteria per unit volume is reduced compared to the case where the denitrifying bacteria are directly dispersed in water as in the comparative example. This is because it can be increased. Specifically, when denitrifying bacteria are directly dispersed in water, it is necessary to adjust the concentration so that the denitrifying bacteria are well dispersed in water when the mixed water is stirred. By being supported on the surface, the microorganisms can flow well together with the carrier in water, so that the microorganisms can be supported on the surface of the carrier at a high density. For this reason, the density | concentration of the denitrification bacteria in a denitrification tank can be made high.
In addition, when the calcium ion density | concentration of treated water was measured, Example 1 and 2 and Comparative Example 1 and 2 did not change with the calcium ion density | concentration of raw | natural water.

  In addition, when denitrifying bacteria are directly dispersed in water, it becomes difficult to effectively separate the denitrifying bacteria in the sedimentation tank, and the denitrifying bacteria flow out to the outside together with the treated water. It became difficult to maintain the concentration of nitrifying bacteria. On the other hand, the denitrifying bacteria supported on the surface of the carrier can be easily separated in the sedimentation tank, and the amount of denitrifying bacteria flowing out can be reduced. It was possible to reduce. For this reason, the density | concentration of the denitrification bacteria in a denitrification tank was able to be maintained favorable.

  Further, when the pH of the mixed water was set to 8 as in Comparative Example 3, the calcium salt precipitated on the surface of the carrier and the stirrer, making it difficult to flow the carrier. That is, in Comparative Example 3, a good fluidized bed could not be formed, the removal rate was remarkably reduced, and the operation of the apparatus became impossible.

  As described above, even with water to be treated containing calcium ions, fluidized bed treatment using denitrifying bacteria supported on a carrier is used and the pH of the mixed water is such that calcium salt does not precipitate. It is recognized that the denitrification treatment can be effectively performed in a state in which the precipitation of calcium salt is suppressed by setting it to (less than pH 7).

  1: Water treatment device, 2: Fluorine treatment unit, 3: Nitrogen treatment unit

Claims (8)

A fluorine treatment part that adds calcium ions to water to be treated containing a fluorine component and a nitrogen component to precipitate calcium fluoride, and removes the fluorine component to obtain first treated water;
In the water treatment apparatus Ru and a nitrogen processor to obtain a second treated water to remove the biologically nitrogen components from the first treated water by microorganisms,
The nitrogen treatment unit includes a nitrification tank that oxidizes ammonia nitrogen in the first treated water by the nitrifying bacteria as the microorganism, and a denitrifying bacterium as the nitrogen component in the first treated water treated in the nitrifying tank. A denitrification tank that reduces by nitrogen and removes it as nitrogen gas,
In the nitrification tank, fluidized bed type treatment using either one or both of a microbial support in which the nitrifying bacteria are supported on a carrier surface and a microbial aggregate formed by aggregation of the nitrifying bacteria themselves is formed. Configured to be performed, and configured to maintain the pH of the mixed water containing the first treated water and the nitrifying bacteria at 5 to 6.5,
The denitrification tank is a fluidized bed type using either one or both of a microbial carrier in which the denitrifying bacteria are supported on a carrier surface and a microbial aggregate formed by aggregation of the denitrifying bacteria themselves. It is configured to perform the treatment, and the pH of the mixed water is maintained to be less than 7 so that the Langeria coefficient of the mixed water containing the first treated water and the denitrifying bacteria is −0.5 to 0. It is comprised in the water treatment apparatus characterized by the above-mentioned. When the proportion of the amount of microorganisms in the nitrogen treatment part is lower than the predetermined proportion with respect to the amount of nitrogen component in the first treated water, the acclimatization is less in the calcium ion content than in the first treated water and contains the nitrogen component. water is introduced to the nitrogen processor instead of the first treated water, configured as a microorganism of the nitrogen treatment unit acclimatization of microorganisms is performed until a predetermined ratio with respect to the nitrogen component amount of the first treated water The water treatment apparatus according to claim 1 , wherein the water treatment apparatus is provided. The water treatment apparatus according to claim 2 , wherein the pH of the mixed water during a period in which the microorganisms are acclimatized is maintained at 7-9. The water treatment apparatus according to any one of claims 1 to 3 , wherein the concentration of calcium ions contained in the first treated water is 200 to 5000 mg / L. A fluorine treatment step of adding calcium ions to the water to be treated containing a fluorine component and a nitrogen component to precipitate calcium fluoride and removing the fluorine component to obtain a first treated water;
In a water treatment method comprising a nitrogen treatment step of biologically removing a nitrogen component from a first treated water by microorganisms to obtain a second treated water,
The nitrogen treatment step includes a nitrification step in which ammonia nitrogen in the first treated water is oxidized by nitrifying bacteria as the microorganism, and a nitrogen component in the first treated water treated in the nitrification step as a denitrifying bacterium as the microorganism. A denitrification step of reducing by nitrogen and removing as nitrogen gas,
In the nitrification step, fluidized bed type treatment using either or both of a microbial support in which the nitrifying bacteria are supported on a carrier surface and / or a microbial aggregate formed by aggregation of the nitrifying bacteria themselves. And maintaining the pH of the mixed water containing the first treated water and the nitrifying bacteria at 5 to 6.5,
In the denitrification step, a fluidized bed using either one or both of a microbial carrier in which the denitrifying bacterium is supported on a carrier surface and / or a microbial aggregate formed by aggregation of the denitrifying bacterium itself. And the pH of the mixed water is maintained at less than 7 so that the Langerian coefficient of the mixed water containing the first treated water and the denitrifying bacteria is -0.5 to 0. Water treatment method. When the proportion of the amount of microorganisms in the nitrogen treatment step is lower than the predetermined proportion with respect to the amount of nitrogen component in the first treated water, the acclimatization has less calcium ions than the first treated water and contains a nitrogen component. 6. The method according to claim 5 , wherein water is used instead of the first treated water, and the microorganisms are acclimatized until the amount of microorganisms in the nitrogen treatment step reaches a predetermined ratio with respect to the amount of nitrogen components in the first treated water. The water treatment method as described. The water treatment method according to claim 6 , wherein the pH of the mixed water is maintained at 7 to 9 during a period in which the microorganisms are acclimatized. The water treatment method according to any one of claims 5 to 7 , wherein the concentration of calcium ions contained in the first treated water is 200 to 5000 mg / L.

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